According to quantum field theory particles are just fluctuations in fields that permeate all of space, so sure.

(The “fabric of spacetime”, on the other hand, is more of a mental analogy than an actual thing.)

You can’t have a space with dimensions if it doesn’t exist in spacetime, so the commonplace understanding of nothingness is a space within spacetime that has nothing that we can interact with that’s interesting to us. People will say that there is nothing in the desert, but there is lots of stuff there. People will say there is nothing in a room, but there is still air. People will say there is nothing in space but there are still diffuse atoms, gravity, radiation and virtual particles. If your definition of nothingness is that there is a space with dimensions and time that has absolutely nothing in, then yes that does not exist.

Historically, “nothing” is the label we apply when none of the things we are currently able to detect are present.

After we can detect what actually is there, we update our description to the much more accurate term “practically nothing”.

Time to rinse off and get out of the shower.